The present invention is directed to welding various materials and will be described hereinafter in conjunction with the welding of metals. It is directed to welding systems such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), fluxed cored arc welding (FCAW), plasma arc welding (PAW), and resistance or spot welding.
The analysis, in real time, of the weld puddle has been attempted with closed circuit television, but the light emitted at the weld is extremely bright, and for various metals there may be insufficient contrast to obtain good definition of the weld puddle. Further, the video scanner must work in a hostile environment where there are sparks and spattering metal. Dirt, dust, and foreign materials may also be present, as well as stray light. Although a video system may be useful in viewing the weld puddle geometry, it still lacks the ability to determine puddle depth and quality, and to provide temperature variation data except through an exterior color analysis of the puddle.
A video system for weld puddle analysis is shown in U.S. Pat. No. 4,595,820 which discloses that video data indicative of some weld conditions can be generated by a video camera directly observing welding operations. According to the technique disclosed in this patent, the width of the weld puddle is monitored by observing local minima of light intensity associated with the edges of the weld puddle. However, this technique or approach is not able to respond effectively to trends of weld speed, current, or resulting puddle geometrics. Further, this approach is not able to recognize conditions below the surface of the weld puddle. This is clear because under video observation, reflected external light is received from the surface of the weld puddle.
Present commercially available adaptively controlled systems that use weld puddle analysis are very limited not only in analysis of the weld, but in their ability to operate in real time at commercially desired speeds, e.g., of nine to twenty-five inches per minute. Typically, current adaptively controlled welding systems using weld puddle analysis operate at a speed of about two to four inches per minute. Current systems further analyze only a few of the variables involved in influencing weld puddle geometry including joint geometry, welding process parameters, chemistry of the materials, and internal defects. In arc welding, the number of process and procedure variables involved in an adaptively controlled welding system becomes particularly large and includes such process variables as heat input, filler wire input, current flow characteristics, shielding gas flow, power supplied (a function of amperage and voltage), material, part position, torch operation, torch position, and torch travel speed. With so many variables, it is little wonder that present day adaptively controlled welders operating at commercial speeds are not able to effectively make an analysis of such a multitude of variables but instead, on occasion, rely upon no more than simple timers and electro-mechanical control arrangements, and monitor simply such parameters as amperage, voltage, and shielding gas temperature. Even the aforesaid patented system analyzes only a few of these processes and procedure parameters or variables, and, nonetheless, operates at a relatively slow weld speed. While laser and video systems for seam tracking are available, they, too, process but a limited amount of information about the seam and the track being followed. These prior art systems also do not, in real time, effectively analyze and assure proper alignment of the torch and joint, and correct effectively for deviations therefrom where the parts are mismatched in the vertical or horizontal directions, or correct for variations in the penetration of the puddle or for the joint root opening between the parts. Further, it would be desirable in real time to be able to make weld size measurements and to correlate them in real time with the mechanical properties of the weld such as tensile and shear strength. In addition to controlling the welding process, it is desirable to have a real time weld inspection system that could determine its physical properties and strength properties. Also, it would be desirable to have a welding system which records and stores information regarding all welding events for later use in the analysis of failed weld joints, analysis of welding consumables used, and welding process conditions encountered when completing a particular weld.
The achievement of a welding system having many or most of the above described features should reduce defects in welds and control weld inspection costs, as well as improve productivity. Such a weld control and weld inspection system requires considerable computing technology. But such systems traditionally require large amounts of computing power and tend to be too slow for real time process control. Accordingly, an object of the present invention is to promote the practical application of artificial intelligence technology to welding process control.
A more general object is to provide a new and improved welding apparatus or method, and to promote the development of adaptively controlled welding techniques, including welding techniques effective for producing high quality welds because of their ability to monitor and control critical processes and procedural variables in real time.
It is an object of the invention herein to adaptively conduct resistance welding, and particularly adaptive resistance spot welding. Adaptive welding techniques generally ensure the creation of better welds. While this does not eliminate the need to consider testing or inspecting the weld after its creation, it is certainly better to do it right the first time. In the case of resistance spot welds, as are particularly useful in the manufacture of automobiles, air frames, aircraft engines, and other sheet metal items, there is frequently no cost effective way to inspect the welds after the fact. Thus, they need to be made correctly the first time. Thus, adaptive control of the weld variables during welding is essential. More automatic production, without in-process inspection and responsive modification of the variables is inadequate.
It is a further object of the invention to more than merely perform seam tracking, but to conduct weld process control and real time weld inspection in the same arrangement for a plurality of weld variables and parameters. Further, it is an object to reduce defects and inspection costs in welding, to improve productivity, to monitor critical process and procedure variables, and to inspect weld defects in real time.